practice problems solutions1

practice problems solutions1 - Single Phase circuit 1) For...

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Unformatted text preview: Single Phase circuit 1) For each following load voltage and current pair find the corresponding power factor and average power absorbed. 277√2 sin 377 30 ; 10 5.1√2 sin 377 30 ; 170 sin 377 8.1 cos 377 30 2) A factory draws 100 A at a 0.7 lagging power factor from a 12.47 kV, 60 Hz line. What capacitor placed across the line at the input to the factory increases the overall power factor to unity? Also, what are the final current for the factory, capacitor and line? Three phase circuit 1) Find the phase currents IBC, IAB, and ICA of a balanced three phase Δ‐load to which one line current is IB = 50 ‐400 A. The phase sequence is ABC. 2) A balanced Y of 20 200 Ω impedances and a balanced Δ of 42 300 Ω impedances are connected by three wires to the secondary of a three phase transformer. If VBC = 480 100 V and if the phase sequence is ABC, find the total phasor line currents. Transformer 1) Consider a 1‐ φ, 10 kVA, 2200/220 V, 60 Hz transformer. Determine the voltage regulation in percent for 75% full load, 0.6 power factor lagging. Draw the phasor diagram. Use the OC test values and SC test values from the below table if required. 2) For the above transformer, consider the test shows the following results. Open circuit test Short circuit test Voltmeter 220 V 150 V Ammeter 2.5 A 4.55 A Wattmeter 100 W 215 W Determine, a) efficiency at 75% rated output and 0.6 pf. b) Power output at maximum efficiency and the value of maximum efficiency. At what percent of full load does this maximum efficiency occur? 3) A 1‐ φ, 100 kVA, 2000/200 V, 60 Hz two winding transformer is connected as an autotransformer as shown in figure such that more than 2000 V is obtained at the secondary. The portion ab is the 200 V winding, and the portion bc is the 2000 V winding. Compute the kVA rating as an autotransformer. ...
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This note was uploaded on 02/11/2012 for the course EEE 360 taught by Professor Gorur during the Spring '08 term at ASU.

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